C3 Hardness of Water

HideShow resource information
  • Created by: Théa
  • Created on: 18-05-13 18:41

What makes water hard?

-MAGNESIUM and CALCIUM IONS cause the hardness of water

-Hard water contains these compunds, which react with soap to form SCUM, however modern 'soapless detergents' do not produce scum in hard water

-The magnesium and calcium get into the water by dissolving when the water flows over rocks containing these compounds

1 of 6

Problems of Hard Water

Scale Formation

-Hard water produces solid insoluble limescale (CaCO3) when heated

-Forms in washing machines, immersion heaters, kettles, etc

-More energy is required to heat things, as the scale creates an insulating layer


-Soap is wasted, reacting with ions, so more is needed to get a good lather

2 of 6

Advantages of Hard Water

-Calcium is good for healthy teeth and bones

-Studies have shown that people who live in areas with hard water have less risk of developing heart disease, probably due to the minerals in the water

3 of 6

Softening Hard Water - Temporary

-Temporary Hardness is caused by hydrogencarbonate ions (HCO3 -)

-It can be removed by boiling, which causes the hydrogencarbonate to decompose

-However this gives scale

4 of 6

Softening Hard Water - Permanent

-Permanent water hardness is caused by calcium sulphate (plus some other things)

-It can be removed by adding 'washing soda', which is sodium carbonate

-Or, it can also be removed by running water through 'ion exchange columns'

-Both these methods also work for removing temporary hardness as well

5 of 6

Softening Hard Water


-Sodium ions which replace the ions removed in the ion exchange columns can cause high blood pressure

6 of 6


No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Water hardness and solubility resources »